20 SCIENCE IN SHORT CHAPTERS. 



There must be a limit, graduated no doubt, but still a prac- 

 tical limit, at which its own atmosphere will leave behind, 

 or pass through, the general atmospheric matter. There 

 must be a heaping or condensation of this matter in the 

 front, a rarefaction or wake in the rear, and a continuous 

 bow of newly encountered atmosphere around the bounda- 

 ries in the opposite direction to that of the sun's motion. 

 The result of this must be that a great portion of the 

 ejected atmospheric matter of the prominences will be 

 swept permanently to the rear, and its place supplied by 

 the material occupying the space into which the sun is ad- 

 vancing. We are thus presented with a mighty machinery 

 of solar respiration; some of this newly arriving atmos- 

 pheric matter must be stirred into the vortices, its quantity 

 being exactly equivalent to that of the old material expired 

 by the explosive eruptions, and left in the rear. 



Now, the new atmospheric matter which is thus encoun- 

 tered and inspired, is the recipient of the everlasting radi- 

 ations whose destination is the subject of Mr. Grove's 

 inquiry; and these, when thus encountered and compressed, 

 will of necessity evolve more or less of the heat which, 

 through millions of millions of centuries they have been 

 gradually absorbing; while, on the other hand, the expired 

 or ejected matter of the gaseous eruptions will, like the 

 artificially compressed air above referred to, have lost all 

 the heat which during its solar existence it had by compres- 

 sion, dissociation, and re-combination contributed to the 

 solar radiations. Therefore, when again fully expanded, it 

 will be cooler than the general medium from which it was 

 originally inspired by the advancing sun. 



The daily supply of fresh atmospheric fuel will be a cy- 

 linder of ether of the same diameter as the sun, and 450,- 

 000 miles in length! I have calculated the weight of this 

 cylinder of ether on the assumption (which of course is 

 purely arbitrary) that the density of the interstellar medium 

 is one ten-thousandth part of that of our atmosphere. It 

 amounts to 14,313,915,000,000,000,000 tons, affording a sup- 

 ply of 165 millions of millions of tons per second; or, if we as- 

 sume the interstellar medium to have a density of only one- 

 millionth of that of our atmosphere, the supply would be 



